1. Field
Apparatuses and methods consistent with exemplary embodiments relate to a transmissive optical shutter and a method of manufacturing the same, and more particularly, to a transmissive optical shutter which may be manufactured at the wafer level and a method of manufacturing a transmissive optical shutter at the wafer level.
2. Description of the Related Art
There is a current trend toward increasing the amount of research for developing a three dimensional (3D) camera, a motion sensor, and laser radar (LADAR), among other things, which can acquire information indicating the distance between the apparatus and an object. In particular, with the development of a 3D display device capable of displaying image depth and an increase in demand for the 3D display device, the importance of 3D content is increasing. Accordingly, research is underway for developing various 3D image acquisition apparatuses with which users may create 3D content.
Depth information regarding the distances between surfaces of an object and a 3D image acquisition apparatus may be obtained by using the time-of-flight (TOF) of light. A TOF method involves projecting a laser beam toward an object and then measuring the travel time taken for the light of the laser beam to be reflected by the object and then received by a light-receiving unit. According to the TOF method, light of a particular wavelength (e.g., near infrared (NIR) light of 850 nm) is projected toward an object by using a light-emitting diode (LED) or a laser diode (LD), a light-receiving unit receives light of the same wavelength reflected by the object, and then a special process for extracting distance information is performed. For example, a phase delay may be measured by amplitude-modulating the reflected light with an optical shutter and then generating an image of the modulated reflected light with an imaging device, such as a charge-coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS) sensor. In other words, by accumulating or sampling the amount of light incident on the imaging device over a predetermined period of time, a brightness image may be obtained, and the phase delay and distance may be calculated from the brightness image. This modulation method involves an optical shutter, which can modulate light at a very high speed, that is, at a frequency of about tens of MHz to about hundreds of MHz, to calculate an accurate phase delay.
Recently, a gallium arsenide (GaAs) semiconductor-based optical shutter, which is easily implemented and may operate at low voltage but at very high speed while being small in size, has been suggested. The GaAs-based optical shutter includes a multiple quantum well (MQW) layer disposed between a P-electrode and an N-electrode, and utilizes a phenomenon by which light is absorbed in the MQW layer when a reverse bias is applied to both the P-electrode and the N-electrode. A GaAs-based optical shutter may be classified as a reflective optical shutter or a transmissive optical shutter. In particular, since the configuration of an optical system is simplified by using a transmissive optical shutter, the use of a transmissive optical shutter facilitates the miniaturization of a 3D image acquisition apparatus.